Main contacts are silver plated copper to silver plated copper. The copper parts are tin plated when in contact with an alu- minum surface. All tinned copper-to-aluminum interfaces are cleaned of oxidation and permanently sealed with an oxydation inhibitor. Self lubricating AgC contacts are available as an option. Contact fingers are self-resilient and do not require any additional springs to provide contact pressure. During a short- circuit, the electrodynamic forces increase contact pressure.